An ion milling method is a processing method for cutting or polishing a sample using a sputter phenomenon in which accelerated ions are caused to collide with a sample to be processed in a vacuum, and the collided ions then sputter atoms or molecules from the sample. In this case, by disposing a mask, which serves as a shielding plate against an ion beam, on the surface of the sample in the beam irradiation direction in advance, it becomes possible to sputter only a portion of the surface of the sample that protrudes from an end surface of the mask, and thus process a smooth sample cross section that is along the optical axis direction of the ion beam.
Such an ion milling method is used to process a metal, glass, ceramics, electronic parts, a composite material, and the like. For example, with respect to electronic parts, such a method is used as a method of fabricating a cross section of a sample to be observed in acquiring an image of the configuration, an image of the sample composition, or a channeling image using a scanning electron microscope (SEM) or the like, or in acquiring X-ray analysis, crystal orientation analysis, or the like, with a view to analyze the internal structure, cross-sectional lamination shape, film thickness evaluation, crystalline state, failure, or a cross section of a foreign substance.
Herein, as a method of fabricating a sample cross section, mechanical processing methods such as a cutting method and a mechanical polishing method are also known. However, there has been a problem that, with such mechanical processing methods, it is difficult to process a composite material containing materials with different hardness and thus eliminate the influence of stress applied thereto, requiring a high skill.
In contrast, an ion milling method, which is a method using a sputter phenomenon of ions, is a sample cross section fabrication method in which physical stress is not applied to a processing target. This method enables processing of a sample that is difficult to be cut or polished mechanically, such as a soft material or a material containing voids.
In an ion milling method, a mask is disposed as a shielding plate on a sample surface in the beam irradiation direction, that is, on the non-processing target region of the sample surface on the beam incident side, and then the sample surface on which the mask is disposed is irradiated with an argon ion beam, for example, to remove a portion of the sample that protrudes from the mask through sputtering, whereby a processed surface that is along the optical axis direction of the ion beam can be acquired. According to such a processing method that applies the ion milling method using an ion beam, it is possible to, even when the sample is a composite material containing materials with different hardness, fabricate a smooth sample cross section with reduced influence of the difference of materials. Further, it is also possible to easily obtain a sample cross section in a smooth and clean mirror surface condition without distortions.
Patent Literature 1 discloses an ion milling device having an ion beam irradiation means disposed in a vacuum chamber for irradiating a sample with an ion beam, a tilt stage disposed in the vacuum chamber and having a tilt axis in a direction substantially perpendicular to the ion beam, a sample holder disposed on the tilt stage for holding the sample, and a shielding material located above the tilt stage for partially blocking the ion beam that irradiates the sample, wherein ion beam sample processing is allowed to be performed by changing the tilt angle of the tilt stage. Patent Literature 1 also discloses a configuration in which an optical microscope for adjusting the position of the sample is attached to the upper end of a sample stage drawing mechanism having the tilt stage attached thereto.
Patent Literature 2 discloses, with respect to an ion milling device, a sample holder for holding a sample as well as a holder fixture for fixing the sample holder on a jig receiving table for a focused ion beam device and a jig receiving table for a scanning electron microscope.